\documentclass{article}
\usepackage{CJKutf8}
\usepackage{amsmath}

\begin{document}
\begin{CJK}{UTF8}{gbsn}

\section{test}
\[	1+2+3/4\times8-9/(4\cdot3)	\]
\[	2^3, 2^{x+y}, T_{9}	\]
\[	\frac{x}{y}	\]
\[	\sum_{k=1}^n \frac{k(k+1)}{2}	\]
\[	\lim_{x\to\infty}f(x)=0	\]
\[	\max_{0\le x \le 1}x(1-x)=1/4	\]
\[
\left|\sum_{i=1}^n a_ib_i\right|
\le
\left(\sum_{i=1}^n a_i^2\right)^{1/2}
\left(\sum_{i=1}^n b_i^2\right)^{1/2}
\]
\begin{align} 
(a+b)^3 &= (a+b)^2(a+b)\\
&=(a^2+2ab+b^2)(a+b)\\
&=(a^3+2a^2b+ab^2) + (a^2b+2ab^2+b^3)\\
&=a^3+3a^2b+3ab^2+b^3
\end{align}


Hello world
Hello world
Hello world

你好

\end{CJK}
\end{document}
